fix: Add missing multiprocessing/resource-tracker type hints

[kkirsche]

X-Ref: #6799

This adds best-effort types to multiprocessing.resource_tracker to begin to address issue #6799

The source file can be viewed here:
https://github.com/python/cpython/blob/main/Lib/multiprocessing/resource_tracker.py

[kkirsche]

It sounds like this is Python 3.8+ only from this error:

error: multiprocessing.resource_tracker failed to import, ModuleNotFoundError: No module named 'multiprocessing.resource_tracker'
Stub: at line 1
MypyFile:1(
  stdlib/multiprocessing/resource_tracker.pyi)
Runtime:
MISSING

Before making changes though, would someone be able to confirm the correct way to address this? I want to avoid unnecessary emails and whatnot as I try to work it out myself

[JelleZijlstra]

You may need to add it to the VERSIONS file if it's new in 3.8.

[kkirsche]

Seems to be the case:
https://github.com/python/cpython/blob/3.8/Lib/multiprocessing/resource_tracker.py
vs. 404 for
https://github.com/python/cpython/blob/3.7/Lib/multiprocessing/resource_tracker.py

Fixed in 274b040

[kkirsche]

Fixed via c74e59c, thank you for the feedback!

[AlexWaygood]

It's true that these methods can be passed literally any object without raising an exception, so your instinct here to annotate these parameters with object was good. However, I feel like it's unlikely that you're actually meant to be passing literally any object to these methods. I think it's more likely that you're meant to be passing some kind of "resource" to these methods (the "shared memory segments, semaphores, etc." referenced in the block comment at the top of the module). I don't know enough about multiprocessing to know what the true type is, so I'd rather we went for _typeshed.Incomplete for now, which serves as an explicit marker of "we're not quite sure what this type should be".

Suggested change

	def register(self, name: Sized, rtype: object) -> None: ...
	def unregister(self, name: Sized, rtype: object) -> None: ...
	def register(self, name: Sized, rtype: Incomplete) -> None: ...
	def unregister(self, name: Sized, rtype: Incomplete) -> None: ...

(You'll have to import Incomplete from _typeshed.)

[kkirsche]

That makes sense, updated :) thanks for explaining that 👍

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉